• Journal of Convergence for Information Technology
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• v.10 no.2
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• pp.32-38
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• 2020

In this paper, we analyze the modulation scheme for high speed transmission in visible light communication system, and study non-orthogonal multiplexing, dimming level and transmission power ratio. Conventional visible light communication has a disadvantage in that it is difficult to multi-transmit to increase the transmission speed. Multi-transmission technique is necessary for high-speed transmission at the transmitter. Since general visible light communication has a limitation in multiple transmission, various researches for high-speed transmission have been conducted. In order to solve this problem, this paper proposes a multiple modulation scheme for high-speed visible light communication using non-orthogonal multiplex transmission scheme and a future research direction.

• Wind and Structures
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• v.34 no.4
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• pp.335-353
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• 2022

The current work numerically investigates the transient force and dynamic response of an overhead transmission tower-line structure caused by the passage of a high-speed train (HST). Taking the CRH2C HST and an overhead transmission tower-line structure as the research objects, both an HST-transmission line fluid numerical model and a transmission tower-line structure finite element model are established and validated through comparison with experimental and theoretical data. The transient force and typical dynamic response of the overhead transmission tower-line structure due to HST-induced wind are analyzed. The results show that when the train passes through the overhead transmission tower-line structure, the extreme force on the transmission line is related to the train speed with a significant quadratic function relationship. Once the relative distance from the track is more than 15 m, the train-induced force is small enough to be ignored. The extreme value of the mid-span dynamic response of the transmission line is related to the train speed and span length with a significant linear functional relationship.

• The Transactions of the Korea Information Processing Society
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• v.1 no.4
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• pp.479-489
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• 1994

At the present time, it is an important problem that we are to select a transmission line code for the very-high speed optical transmission system which can confidentially transfer the original information signal sequence efficiently, as it is to be the large capacity and the economization for the optical digital transmission system to transfer the information signal sequence at the very-high speed. Therefore, this paper is to select first the proper transmission line codes for the high speed(more than Mb/s) optical transmission system of the proposed two-level unipolar transmission line codes up to date, and to decide a mBIZ (m Binary with One Zero insertion) code as an optimal transmission line code for the very-high speed optical transmission system, resulting from analyzing the performance at the requirements of the transmission line code, such as the maximum consecutive identical digits, the transmission delay time, the increasing rate of clock, the mark rate, the circuit complexity, the supervision of transmission line error, and power spectrum among the selected transmission line codes.

• Journal of Communications and Networks
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• v.5 no.1
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• pp.25-32
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• 2003

4G mobile communication system requires the throughput of 10-100Mbps. Adaptive modulated OFDM system is promising technique for increasing the throughput. In the pilot symbol assisted high-speed packet transmission system, the data symbol duration is generally considered to be small compared to the coherence time. However, OFDM symbol duration is longer than the symbol duration of a single carrier system, so that the packet duration of the pilot symbol assisted high speed packet transmission system is long. In this case, the change of channel conditions is too fast to be accurately estimated by channel estimator at the receiver in high Doppler frequency, so that many errors occur during demodulation, especially with the data symbols at the end of each packet. In this paper, we consider the BER at various instantaneous $E_b/N_o$ that includes the demodulation errors in high Doppler frequency. When the coherence time is ten times longer than the duration of a single packet, the channel can be closely approximated as an AWGN channel. Otherwise, the approximation breaks down and the above-mentioned errors that occur during demodulation must be taken into consideration. In this paper, we propose the pilot symbol assisted high speed packet transmission system based on adaptive OFDM using a novel lookup table to consider the demodulated errors and evaluate the throughput performance.

• Information and Communications Magazine
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• v.11 no.2
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• pp.77-89
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• 1994

High speed optical fiber transmission technology has been remarkably improved during the past 20 years. This paper presents recent research status and future technological issues for the future information society, that is, the Tb/s transmission by frequency division multiplexing and the ultra long-distance by optical soliton transmission. Erbium-doped fiber amplifier and recent optical technology have brought optical transmission system of up to 10 Gb/s to the point of commercialization. Taking into account the future super information highway, that is, B-ISDN network, ultra wide-band picture-based information can be provided for many subscribers via existing optical fiber cables. However, to achieve the high speed transmission, the technologies must be developed not only for transmission lines but also for transmission nodes. Since the conventional signal transmission/processing technique using electronics has the limit in its speed, novel photonic technology is being developed for this purpose. On the other hand, optical solitons propagate stably through optical fibers, without pulse broadening effect of the fiber dispersion. Since the pulse broadening effect becomes serious as the transmission speed increases, optical solitons is the important technologies to realize the high speed, long distance transmission.

• Journal of information and communication convergence engineering
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• v.6 no.2
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• pp.192-197
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• 2008

High-speed harmonic optical modulation-demodulation schemes are presented and a possibility of the schemes for applying to high-speed light wave transmission system is tested at microwave frequency range. An example of this concept is as follows : Light wave is modulated succeedingly through cascaded optical modulators by a sub-carrier to produce a modulated light wave at harmonic frequency which is higher than the feasible frequency of the individual modulators. For demodulation of the base-band signal, the high frequency optical sub-carrier is down-converted by the same kind of optical modulator with the same concept of harmonic modulation.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.8
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• pp.843-852
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• 2006

Vibration/noise analysis as well as strength of planetary gear train are considered in order to develop a transmission for a high-speed ship. The vibration model of a gear pair is developed with considering the elastic deformation of the active teeth and the body to be a rigid. Excitation forces of the transmission system are considered as the mass unbalance of the rotors. misalignment and a function of gear transmission error which comes from the modified tooth surface. A Campbell diagram, in which the excitation sources caused by the mass unbalance of the rotors. misalignment and the transmitted errors of the gearing are considered shows that, at the operating speed, there are not the critical speed.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.1
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• pp.42-47
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• 1999

This paper presents the information transmission between on-board and ground-site in MAGLEV. considering safety and high speed operation and density operation, information transmission between them is necessary. Therefore it is necessary for transmission system to ensure high speed transmission, low error rate, massive information, and reliability of information. To provide above conditions, 1.1km signal line assembly was constructed and Frequency Shift Keying(FSK) modulation and Open System Interconnection(OSI) based high-level data link control(HDLC) protocol are applied. To modulate digital signal for transmission from ground-site to on-board, carrier frequency of 70kHz is used and 90khz is used for transmission from on-board to ground-site. Transmission speed is 2400bps for consideration of train speed, quantity of information, and data error rate. And this paper introduces information monitoring considering user interface and presents the method for an effective data transmission in MAGLEV which is now being tested and intends to provide for an intelligent train operation system in future.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.7
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• pp.148-157
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• 1995

This study deals with controlling the speed of Hydrostatic Transmission (HST) system throuth the control of pumping stroke of positive displacement pump using high-speed solenoid valve controlled by digital closed loop PWM method. The method which was done in this study is as follows: First, we modified original positive displacement pump and designed pumping stroke control system of HST by using the high-speed solenoid valve. Second, after experimenting static and dynamic characteristics on each signal flow, we identified system parameter of approximated model. Finally, to control the speed of HST, we controlled the angle of the swash plate of positive displacement pump by controlling the pressure in the control cylinder chamber. Test which was carried out in the laboratory shows that transient and steady state response could be improved by PID controller.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.6
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• pp.1374-1381
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• 1994

This study suggests a new type shaft generating system driven by hydrostatic transmission suitable for small size vessels. In this system, the hydraulic motor speed is controlled by displacement adjustment using a 3-way high speed on/off valve. The 3-way high speed valve is operated by PWM control signal. In this study, a digital robust servo control algorithm is applied to the controller design of the system. By experiments and numerical computations, the frequency variation characteristics of the generating system under various disturbances are investigated. Conclusively, it is said that the shaft generating system proposed in this study shows excellent control performances.